The US will now extend the same visa privileges worldwide to gay married couples as to heterosexual spouses, Secretary of State John Kerry has said.

Speaking at the US embassy in London, Mr Kerry announced such applications would all be "treated equally".

The move comes just over a month after the US Supreme Court struck down a key part of a law that defined marriage as between a man and a woman.

The Obama administration ordered federal agencies to comply.

Speaking shortly after his arrival in London, Mr Kerry said: "When same-sex couples apply for a visa, the Department of State will consider that application in the same manner that it considers the application of opposite sex spouses.

"If you are the spouse of a US citizen, your visa application will be treated equally. If you are the spouse of a non-citizen, your visa application will be treated equally.

"If you are in a country that doesn't recognise your same-sex marriage, then your visa application will still be treated equally at every single one of our 222 visa processing centres around the world," he added.

Last month, the US immigration agency announced it would begin considering applications filed in the US on behalf of same-sex spouses the same way as those for spouses in heterosexual marriages.